Free-standing audio-visual-response teaching system

ABSTRACT

A PROGRAMMING COMPONENT GENERATES SELF-CLOCKING DIGITAL CONTROL SIGNALS AND RECORDS THEM ON ONE TRACK OF A MAGNETIC TAPE AND RECORDS ANALOG SIGNALS ON ANOTHER TRACK FOR PROVIDING AUDIO INFORMATION TO THE STUDENT. THE TAPE IS THEN UTILIZED IN A RESPONSE COMPONENT WHICH RESPONDS TO THE DIGITAL CONTROL SIGNALS TO PROVIDE AUTOMATIC OPERATIONS SUCH AS REMOTELY OPERATING ONE OR TWO VISUAL DISPLAY DEVICES (I.E., A SLIDE PROJECTOR), FOR PRESENTING TO THE STUDENT MATERIAL IN LECTURE FORM AND, OR, MULTIPLE-CHOICE PROBLEMS. THE RESPONSE COMPONENT INCLUDES ELECTRONIC LOGIC CIRCUITRY FOR DETERMING THE CORRCTNESS OF THE STUDENT&#39;&#39;S RESPONSE TO THE PROBLEMS. A PUSHBOTTOM ASSEMBLY ON THE RESPONSE COMPONENT PERMITS THE STUDENT TO ADVANCE THE TAPE IN ACCORDANCE WITH THE TAPE RECORDED PROGRAM AND TO INDICATE HIS ANSWERS TO THE PROBLEMS. THE RESPONSE COMPONENT IS INTENDED FOR INDIVIDUALIZED INSTRUCTIONS WITH TOTALLING OF THE STUDENT&#39;&#39;S RIGHT AND WRONG RESPONSES BEING DONE ON COUNTERS MOUNTED ON THE RESPONSE COMPONENT.   D R A W I N G

March 6, 1973 Filed April 1, 1971 T. L. HEWITT FREE-STANDINGAUDIO-VISUALRESPONSE TEACHING SYSTEM 6 Sheets-Sheet l F/ a/a RecordPushbutton /5 x7 Relay Record mum MlllPflPl/ME Tape WW Re cor der l0Fl/tr and Relay Delay J3 PROGRAM 1WD LAMP l5 Contro/ Track 519mlGenerator PMJ 4: 3} we JZ/flt' P1901.

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m WM T. L. HEWITT March 6, 1973 FREE-STANDING AUDIO-VISUAL'RESPONSETEACHING SYSTEM Filed April 1, 1971 6 Sheets-Sheet 4 lnrenbar I Terry 1.Hewitt T. L. HEWITT March 6, 1973 FREE-STANDING AUDIO-VISUAL-RESPONSETEACHING SYSTEM Filed April 1, 1971 6 Sheets-Sheet 6 N mi Invent orTerry 1 He witb by Q .7llmfl4 United States Patent 3,718,984FREE-STANDING AUDIO-VISUAL-RESPONSE TEACHING SYSTEM Terry L. Hewitt,Schenectady, N.Y., assignor to General Electric Company Filed Apr. 1,1971, Ser. No. 130,397 Int. Cl. G09b 7/06 U.S. Cl. 35-9 A 21 ClaimsABSTRACT OF THE DISCLOSURE A programming component generatesself-clocking digital control signals and records them on one track of amagnetic tape and records analog signals on another track for providingaudio information to the student. The tape is then utilized in aresponse component which responds to the digital control signals toprovide automatic operations such as remotely operating one or twovisual display devices (Le, a slide projector), for presenting to thestudent material in lecture form and, or, multiple-choice problems. Theresponse component includes electronic logic circuitry for determiningthe correctness of the students response to the problems. A pushbuttonassembly on the response component permits the student to advance thetape in accordance with the tape recorded program and to indicate hisanswers to the problems. The response component is intended forindividualized instruction with totalling of the students right andwrong responses being done on counters mounted on the responsecomponent.

My invention relates to a teaching system which features audio, visualand multiple-choice response capabilities, and in particular, to asystem in which the response component thereof is adapted forindividualized instruction.

The present application is related to application S. N. 130,386entitled, Scanned Audio-Visual-Response Teaching System, and toapplication S. N. 130,391 entitled, Group Instruction Audio-VisualTeaching System, concurrently filed with the present application, havingthe same inventor and assigned to the assignee of the present.

Various techniques are currently being proposed for aiding instructorsin their teaching assignments for purposes of increasing theirproductivity and thereby making it possible for each instructor to teachmore students. One of the prior art approaches is the computer-assistedinstruction in which a computer is programmed to print out questions andthe student literally talks with the computer in providing his answerand is informed of its correctness. The disadvantage of thecomputer-assisted instruction is the fact that it is very expensive, ismost often not provided with audio or visual capabilities, and requiresa teletype unit for each student. Other more recent teaching systemsinclude the combination of a phonograph record and slides which has thedisadvantage in that the phonograph record is provided with a fixedprogram and therefore thesystem is not readily programmable.

Therefore, a principal object of my invention is a teaching systemhaving an audio, visual and student response capability and adapted forindividualized instruction.

Another object of my invention is to provide the system with a componentfor readily programming a particular assignment with minimum complexityand low cost.

A further object of my invention is to provide the programming componentwith a conventional two track magnetic tape recorder whereinself-clocking digital control signals are recorded on one track andanalog signals on another track.

A still further object of my invention is to provide the responsecomponent of the teaching system with the abil- 3,718,984 Patented Mar.6, 1973 ity to remotely operate one or two visual devices which presentthe teaching assignment to the student.

Another object of my invention is to provide counters on the responsecomponent for totalling the right and wrong responses of the student toquestions presented in the lesson.

Briefly stated, my invention is a teaching system which includes aprogramming component and a response component adapted forindividualized instruction. The programming component includeselectronic logic circuitry for generating self-clocking digital controlsignals which are recorded on one track of a magnetic tape, and furtherincludes an audio input for recording analog signals on another trackfor providing audio information to the student. The tape from theprogramming component is then utilized in the response component whichresponds to the digital control signals to provide automatic remoteoperation of one or two visual display devices that presentinstructional material to the student. The response component includeselectronic logic circuitry for determining the correctness of thestudents response to problems presented in the instruction material, andcounters for totalling the students right and wrong responses. Apushbutton assembly on the response component permits the student toadvance the tape and indicate his answers to the problems.

The features of my invention which I desire to protect herein arepointed out with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings wherein like parts in each of the severalfigures are identified by the same reference character, and wherein:

FIG. 1a is a block diagram of the programming component of my teachingsystem, and FIG. 1b illustrates the control panel thereof;

FIG. 2 is a detailed block diagram of the control track signal generatorillustrated in FIG. 1;

FIG. 3a is a general block diagram of the response component of myteaching system, and FIG. 3b illustrates ,the control panel of theresponse component;

FIG. 4 is a detailed block diagram of the response component;

FIG. 5 is a block diagram of the pushbutton assembly illustrated inFIGS. 3a and 4;

FIG. 6 is a detailed block diagram of the control track amplifierillustrated in FIG. 4, and

FIG. 7 is a detailed block diagram of the control logic illustrated inFIG. 4.

The teaching system in accordance with my invention includes aprogramming component and a response component. The programmingcomponent permits an instructor to prerecord a lesson on a conventionaltape recorder by recording the requisite audio information on the firsttrack of a magnetic tape in the form of analog signals. The instructorthen rewinds the tape, plays back the audio, and records self-clockingdigital control (command) signals on a second track of the tape atappropriate points in the audio program. The digital control signalsdirect the operation of one or two visual display devices such as aslide projector or other device capable of presenting a visual displayto the student. The digital control signals also cause the responsecomponent to stop after a question has been presented to the student on.the visual device display and/or on the audio track of the magnetictape. Upon the stop in the response component operation, the studentpresses one of a series of five buttons on the response componentcontrol panel, indicating his choice of an answer to the questionpresented. A correct answer is indicated by a light on the responsecomponent control panel and the student is then permitted to proceed tothe next part of the lesson. An incorrect answer prevents the responsecomponent from advancing the tape to the next part of the assignment andtherefore requires the student to press another of the five buttonsuntil he has found the correct answer. Counters mounted on the responsecomponent, but preferably out of view of the student, total his correctand incorrect answers.

Referring now in particular to FIG. 1a there is shown a block diagram ofthe programming component and FIG. 1b illustrates a typical controlpanel provided on the programming component. The programming componentas well as the response component are each of small size, portable, andeach includes an identical conventional cassette tape recorder 10. Thedigital control signal is coded to provide eight different commands,namely, STOP, for causing the tape recorder to stop, SLIDE, for causingan advance in the visual display device, five for storing answers tomultiple-choice questions presented in the lesson, and a PRO]. 2 commandfor operating a second visual device, or the like. The digital controlsignal commands are entered simply by pressing and releasing theappropriate one of eight pushbuttons 13a-h on the control panelillustrated on FIG. 1b and labeled SLIDE, STOP, 1, 2, 3, 4, 5 and PROJ.2, respectively. Errors in the program may be corrected by theinstructor on either the audio or digital track, without affecting theother track, by rewinding past the point of error and then rerecording.

One of the novel aspects of my invention is the particular type ofdigital control signals employed for providing particular automaticoperations of the response component. Prior art cassette tape recordersutilize audio signals alone or audio with a single tone for the remoteoperation of a slide projector wherein the signal tone is superposed onthe audio track as an inaudible tone or is recorded on a second track,the tone also adapted for film advance and for stopping operation of theresponse component.

My use of the aforementionedvcoding of the digital control signalpermits a very simple programming pro cedure which may be utilized by aninstructor having no technical experience in programming therebyrendering my teaching system very versatile. The tape recorder utilizestwo-channel, two-track record/ playback and erase heads, although theresponse component tape recorder requires only a two-channel, two-trackrecord/playback head and one-channel, two-track erase head. The use oftwo-channel, two-track playback and erase heads in the programmingcomponent tape recorder permits the following operations: audio recordand erase, audio playback, audio playback and digital record and erase.Sufiicient separation is provided on the magnetic tape between the twochannels for isolation between the audio and digital playback signals.

The digital control signals are initially of square wave form, thesquare waves being generated in a control track signal generator 11.Frequency shaping of the square wave is accomplished in a conventionalfilter and delay network 12 which includes high and low pass filters toprovide a frequency response peaking at approximately 1000 Hertz. Adelay circuit in network 12 delays the start of the recording of thedigital control signal for approximately one second after the start ofthe erase signal to assure that the digital signal will always berecorded on erased tape when reprogramming the digital track.

The digital control signal is of the pulse-width-modulated type referredto as 2/6 PWM. In this format, a logic ZERO is represented by a pulsewhich is 2/8 of a period long, and a logic ONE is represented by a pulsewhich is 6/8 of a period. The leading edge of each pulse is at a commonrepetition rate and therefore includes the clock information while thepulse width determines whether the bit is a logic ONE or ZERO. The pulsewidth modulated signal is generated in the control track signalgenerator 11 which is described in a more detailed block diagram in FIG.2. The digital PWM signal is recorded continuously on the second(control) track of the magnetic tape and appears as a series of logicZEROES at all times other than during the time a command is beingrecorded. As each command is entered, the corresponding digital word isrecorded twice with a short time lapse separating the two words to makemore certain that at least one of the words is detected during playback.Logic in the response component prevents the second word having anyeffect if the first word is detected. Six bit words are used to encodeeach of the eight commands utilized in my system. Each of these eightwords has logic ONES as the first and sixth bits as a requirement fordetection of a valid word in the playback logic of the responsecomponent. The remaining four bits are encoded such that any single biterror will be ignored by the detection logic. Thus, the code is asfollows:

ANSWER 1: 100011 ANSWER 2: 100101 ANSWER 3: 101001 ANSWER 4: 101111ANSWER 5: 110001 PROJECTOR NO. 2: 110111 SLIDE ADVANCE: 111011 STOP:111101 The cassette tape recorder 10 is provided with five pushbuttonsand one knurled volume control 10f as illustrated in FIG. 1b.Pushbuttons 10a, 10b, 10c and 10d are labeled STOP, REWIND, FASTFORWARD, and PLAY AND RECORD, respectively. Pushbutton 10a is labeledRECORD and must be depresed along with the PLAY AND RECORD pushbutton10d when recording audio in the programming operation.

The programming component includes the cassette tape recorder 10 andprogramming unit 13. All of the elements in FIG. 1a. except for taperecorder 10 are elements of the programming unit 13. The digital signalproduced in control track signal generator 11, with each command enteredvia a corresponding command pushbutton 13a- 1311, is passed throughfilter and delay network 12 and relay 14, and finally to the digitalrecord channel of the record/playback head on the tape recorder. Relay14 is a 6-pole relay energized (driven) by a transistor circuit 15during the digital record mode upon the depression of the (digital)RECORD pushbutton 16 on the pro gramming unit. The first contacts ofrelay 14 switch the digital signal to the digital track of therecord/playback head, the second contacts direct a high frequency recordbias signal commonly used in audio recording to the appropriate audio ordigital track of the record/playback head, the third contacts interruptan audio signal path in the recorder to prevent interference with thedigital recording, the fourth contacts direct the erase signal to theappropriate audio or digital track of the erase head, the fifth contactsswitch on an audio oscillator in the tape recorder during digital recordwhich provides the high frequency signal for both the erase and biasfunctions, and the sixth contacts latch the relay in the digital recordmode after the digital RECORD button 16 on the programming unit ismomentarily held down and the tape recorder PLAY AND RECORD button 10dis also depressed, resulting in the tape recorder operating and therelay 14 being energized and latching, and the digital signal then beingrecorded. The relay 14 switching functions are used in order to utilizethe circuitry existing in the conventional tape recorder 10 for bothaudio and digital control signal recording. The digital record mode isindicated by the lighting of RECORD indicator lamp 17, energized by therelay driver circuit 15. A PROGRAM indicator lamp 18 is lit for severalseconds after a digital command signal has been recorded to verify suchoperation. A CANCEL pushbutton 13i permits an erroneously pressedcommand pushbutton 13a-13h signal to not be recorded. Upon the stoppingof the tape recorder by depressing STOP pushbutton 10a, the relay 14 isunlatched and the contacts thereof return to the nonenergized state ofthe relay.

Referring now to FIG. 2 there is shown a detailed block diagram of thecontrol track signal generator 11 illus' trated in FIG. 1 which producesthe digital control signal in response to each command entered by meansof a corresponding program command pushbutton (PROG. COMM. PB) 13a-13h.The output of the control track signal generator (output of PWMgenerator 27) is the digital control signal in the above-described 2/ 6PWM format which is then passed through filter and delay network 12 andthence to the digital record channel of the record/playback head viarelay 14.

The control track signal generator 11 comprises the majority of thecircuitry in the programming unit 13 and can conveniently be containedon one printed circuit board. The repetition rate of the digital controlsignal is -00 bits per second (b.p.s.) and is determined by aconventional free-running 2000 b.p.s. multivibrator circuit 20, and aconventional divide-by-four counter circuit 21 connected to the outputof the multivibrator for reducing the repetition rate to 500 b.p.s. Aconventional six-bit sequence generator 22 is clocked at the 500 b.p.s.rate from the output of the divide-by-four counter 21. Sequencegenerator 22 may conveniently include three dual flipflops with all theoutputs held in the high state (logic one) at all times except when acommand is entered. The command is entered by means of the ENABLE inputto sequence generator 22 from the output of a flip-flop circuit 23a. Asstated hereinabove, a program command is initiated by pressing one ofthe command pushbuttons 13a- 13h. Each of the eight pushbuttons providesan input to the SET(S) input of a corresponding command flip-flop 24(i.e., there are eight flip-flops 24 in the eight sections indicated bydashed outline) which are normally in the reset state. Pressing one ofthe command pushbuttons 13a-13h causes the associated flip-flop 24 tohave its SET input switched to ground potential whereby the output ofthe flip-flop is set to the high state. The pushbutton input from eachof the eight pushbuttons is also supplied to one OR gate 25 such thatwhen any one of the pushbuttons is depressed, the output of gate 25 isswitched to the low state. The output of OR gate 25 is connected to theSET input of the enable flip-flop 23a.

Thus, with any one of the command pushbuttons 13a- 13h depressed, theoutput of OR gate 25 goes low and sets the enable flip-flop 23a to causeits output to go high. The output of enable flip-flop 23a is one inputto AND gate 23b. The second input to gate 23b is from the output of ORgate 25. In this Way, the ENABLE output of AND gate 23b is prohibitedfrom going high until the COM- MAND pushbutton is released. The outputof AND gate 23b causes the sequence generator 22 to produce a six bitsequence output, the sequence beginning in state 111111 and proceedingthrough a sequence which provides all 63 possible states excluding theall-zero state (000000). The appropriate point in the sequencecorresponding to the particular one of the pushbuttons 13a-13h which hasbeen depressed, is determined by the eight AND gates 26 having inputsconnected from the outputs of command flip-flops 24 and sequencegenerator 22. The outputs of the eight AND gates 26 are connectedtogether, the common connection is connected to the SET input of aflipflop 29, and the output thereof connected to an input of AND gate28. AND gate 28 has its second input connected to the output of the6-bit sequence generator 22, and thus, the desired digital word codecorresponding to the particular depressed command pushbutton is obtainedby gating the output of the sequence generator 22 through AND gate 28 atthe appropriate point in the sequence at which the desired word codeappears. This allows the output from the sequence generator 22 to passthrough to the pulse-width-modulation (PWM) generator 27 via AND gate 28for six clock pulses only. The output from flip-flop 29 also isconnected to AND gate 30 which has its second input supplied with the500 b.p.s. CLOCK pulses developed at the output of divide-by-fourcounter 21. The output of gate 30 is thus a gated CLOCK signal which issupplied to a divide-by-six counter 31. After six clock pulses haveoccurred, counter 31 produces an output which resets flip-flop 29 (theoutput of counter 31 is connected to the RESET (R) input of flip-flop29) and thereby closes gate 28. This sequence of events permits only sixoutput PWM pulses to appear at the output of PWM generator 27 and thenreturns the output of PWM generator 27 to a sequence of all zeroes.

The output of the particular flip-fiop 24 associated with the SLIDEadvance command pushbutton 13a is also connected to the input of aone-shot (multivibrator) 32 which produces a pulse signal initiatingoperation of the slide projector or other visual display device, and inthe case of the slide projector, the signal causes the slide projectorto advance one slide. The output of the flip-flop 24 associated with thePRO]. 2 pushbutton 13h, if used, can initiate operation of a secondvisual display device such as a movie projector, as one example.

The CANCEL pushbutton 13i is connected to the common RESET line for theeight flip-flops 24 and thus is a normally open contact which, whenclosed upon depression of the CANCEL pushbutton, causes the RESET lineto be at ground potential thereby resetting any command flip-flops 24which had been set, and also resetting the enable flip-fiop 23a. TheCANCEL pushbutton 13i is only effective if it is pressed down while acommand pushbutton 13a-13h is being held down since once the commandpushbutton is released, the digital word code generation begins (i.e.,the digital word code is not generated until the command pushbutton isreleased).

The purpose of the serially connected divide-by-two counter 33(connected to the output of flip-flop 29) and pulse circuit 34 are torecord each digital command word twice as mentioned hereinabove. Thecommand fiip-flops 24 and enable flip-flop 23a are reset after thecommand has been twice recorded, in response to a pulse produced incircuit 34. One-shot 35 connected to the output of counter 33 lightsPROGRAM lamp 18 to verify that the command word has been entered(recorded).

Referring now to FIG. 3a, there is shown a block diagram of the responsecomponent, and FIG. 3b illustrates a typical control panel provided onthe response component. The response component includes a cassette taperecorder 10 and a response unit 39. The tape recorder 10 is similar tothe tape recorder employed in the programming component with theexception that no microphone input is required. An earphone output isutilized by the student for listening to the audio information recordedon the first track of the: magnetic tape as prepared by the instructor.

A seven pushbutton assembly is used by the student for operation of theresponse component. The seven pushbuttons are more clearly seen on thecontrol panel view of FIG. 3b and include START button 42a and fiveMULTIPLE CHOICE (MC) buttons 42b-42f. The seventh pushbutton is the PLAYAND RECORD pushbutton 10d on the tape recorder 10 of the responsecomponent.

The student starts the program by pressing the PLAY AND RECORD button10d on the tape recorder 10 to thereby place the response component in astandby mode with the tape drive off. The lesson in the program isactivated by pressing the START button 42a on the response unit, therebyinitiating the. audio portion of the program as well as the digitalportion. The contacts of the START and MC pushbuttons 42a-42f,respectively, are connected directly to the pushbutton assembly printedcircuit board (PB assembly PC board) 43, these pushbutton elements beingillustrated in greater detail in FIG. 5. Circuitry on the PB assembly PCboard 43 is connected to control logic circuitry 41 which detects anddecodes the digital signals for performing the operations dictated bysuch digital signals. The digital control signal is transmitted from thetape recorder to control logic circuitry 41 by way of a control trackamplifier 40.

Thus, upon activation of the START button 42a, the lesson begins, and asone example, the lesson may include a presentation of a first slide,followed by a second slide containing a question and having one of fivemultiplechoice answers. The first and second slides are successivelypresented on a screen automatically in response to first and secondSLIDE advance command digital control signals programmed on the tape.The audio which accompanies the slides may instruct the student toanswer the question by pressing one of the five MC buttons 42b-42f. Aprogrammed STOP digital command signal at the end of this audio messageautomatically stops the tape with the second (question) slide presentedon the screen. The student now presses one of the five M'C buttons, andif his answer is correct, the control logic 41 causes a RIGHT indicatorlamp 44a to light. If his answer is wrong, a WRONG lamp 44b lights. Thestudent must continue pressing additional MC buttons if his firstselection was wrong, until he obtains the correct answer, and only afterthe correct answer will he be allowed to continue the lesson. A pair of3-digital electro-mechanical counters 48a, b are preferably mounted onthe rear of the response unit in order to be out of view of the student(although they can be mounted to be in his view if so desired), haveinputs connected to control logic 41, and indicate the students totalnumber of right and wrong answers. An AUTOMATIC/ MANUAL switch 45determines whether the operation of the response component isautomatically controlled by the digital control signal and internallogic. Switch 45 is preferably located on a rear panel of the responseunit. In the MANUAL position of switch 45, the response componentoperation is not automatically controlled.

Referring now to FIG. 4, there is shown a detailed block diagram of theresponse component. The digital control signal recorded on the secondtrack of the magnetic tape is read off by the playback head of taperecorder 10 and is supplied to the input of control track amplifier 40which includes an amplifier section 40a and level detector section 40b.The details of the control track amplifier 40 are illustrated in FIG. 6.The amplifier portion 40a includes an automatic level control circuit tomaintain the amplifier output at a reasonably constant level. The leveldetectors 4% detect the positive and negative portions of the amplifier40a output signal and thereby reconstruct the CLOCK and DATA (PWMgenerator 27 output) components which form the original PWM signal. TheCLOCK and DATA signals at the output of level detectors 40b are suppliedto 6-bit shift register circuitry 41a in the control logic 41 portion ofthe response unit. Outpus from the first and sixth stages of the shiftregister are supplied to a Word detector and delay gate circuit 41b asthe first step in extracting the eight command word codes from thedigital control signals. A high state output from circuit 41b isproduced only when the first and sixth bits are simultaneously highwhich is a characteristic of the code format described hereinabove andis the first criteria for detection of a valid word. The word detectorcircuit 41b output and the outputs from the other four stages of theshift register 41a, bits two through five, are the inputs to four logiccircuits 41c, 41d, 41e and 41i. The SLIDE word is decoded in the slideadvance circuit 410 and results in an output pulse which turns on asilicon controlled rectifier that supplies power to the slide projectorto cause it to advance one frame. The STOP word is decoded in the taperecorder play control circuit 41d and results in turning off the taperecorder 10 motor.

8 The binary words for the five MULTIPLE CHOICE answers are decoded inthe word decode circuit 41e. The PRO]. 2 word is decoded in circuit 41i.

The delay gate portion of circuit 41b prevents the detection of anerroneous command during periods in which the digital signal is not in asteady-state condition. These periods are usually marked by a transient,noisy signal which occurs whenever the tape recorder starts or stops,and also at the start of the recorded digital signal on the digitaltrack due to the start-up of the tape recorder in the programming unit.The delay gate responds to the CLOCK pulses from the clock leveldetector 40b, and if no CLOCK pulses are being received, the delay gateholds the output of the word detector 41b both when the tape recorder isstopped and when the tape is moving but there is no recorded signal onthe digital track. 'Upon the arrival of a CLOCK signal, the delay gatecauses a delay of several seconds before the hold is removed from theword detector output in circuit 41b.

The prevention of detection of an erroneous command during the slow downcondition of the tape recorder when it is being stopped is accomplishedby means of an input to the delay gate from the tape recorder playcontrol circuit 41d. Thus, when tape recorder play control circuit 41dreceives a STOP command, delay gate 41 produces an immediate hold on theword detector 41b output.

The CLOCK pulse is also used for inhibiting the gating action of logicgates in the word detector circuit 41b in the case wherein such gatescould produce false outputs if sampled at the time the shift register isbeing clocked. This false operation is due to the normal time delays inthe logic circuitry and inhibiting these gates from responding at thetime of the shift register transitions remedies this false operation.

As the digital control signal is propagated through the shift register41a, a series of gates in the word decode circuit 41e receive theirinputs from the outputs of the second through fifth stages of the shiftregister and respond to the codes which correspond to the MULTIPLECHOICE answers. When any one of the five MULTIPLE CHOICE codes isdetected, a flip-flop in the operation logic circuit 41] is set andcauses a quad latch to hold the information contained in thebits twothrough five at that time, this information being held until reset bysignals developed in a confirmation logic circuit 41g connected to theoutput of the word decode circuit 412. The resetting by the confirmationlogic occurs after a correct answer to an MC question is submitted bythe student. Thus, once a MULTIPLE CHOICE signal is detected, the worddecode circuit 41e holds the associated information until the taperecorder has stopped and the student has made the necessary responsecalled for by the program.

The output from word decode circuit 41e to the confirmation logiccircuit 41g consists of one line for each of the five possible MULTIPLECHOICE answers. The students choice is made through the pushbuttonassembly 42, 43 and is compared with the correct answer in theconfirmation logic 41g. The RIGHT and WRONG indicator lamps 44a and 44b,respectively, are operated by the output of confirmation logic circuit41g, and are lit in accordance with the correctness of the studentschoice. In like manner, the electro-mechanical RIGHT/ WRONG counters48a, b are operated by the output of confirmation logic circuit 41gthrough RIGHT/ WRONG (R/W) counter drivers 41h. The RIGHT/ WRONGindicator lamps provide a visual indication to the student of thecorrectness of his answer. An input from the AUTO/MANUAL switch 45disables the confirmation logic when the switch is in the MANUALposition thereby prohibiting operation of the RIGHT/ WRONG indicatorlamps.

The operation control logic developed in circuit 41 provides constraintson operation of the teaching system to assure proper operation thereofby the student. Two fundamental operations which are controlled bycircuit 41 are those associated with the START pushbutton 42a and thefive MULTIPLE CHOICE (MC) pushbuttons 42b through 42 In each case, theoperation control logic circuitry maintains (holds) the state in whichthe response unit is to operate as determined by the interaction betweenthe student, the teaching system and the taped program.

Each time the START pushbutton 42a is depressed, the START output fromthe pushbutton assembly 42, 43 is supplied to the tape recorder playcontrol circuit 41d. However, the output from the operation controllogic 41] determines whether the START signal will be able to start thetape recorder.

A first hold condition requires the detection of a MULTIPLE CHOICE (MC)word code in the word decode circuit Me. A MULTIPLE CHOICE word outputfrom the word decode circuit to the operation control logic 41f preventsrestart of the tape recorder until the student makes the first correctresponse to a multiple choice question. After the student has made thecorrect response to a multiple choice (MC) question, the MC pushbuttons42b through 42 are disabled whereby the only option left to the studentis to restart the tape recorder and continue the program.

A second hold condition is the operation of either of the RIGHT/WRONGindicator lamps 44a, 1:. Thus, after the student makes a choice, if aRIGHT or WRONG indicator light comes on, he cannot restart the taperecorder or make another choice until the light has gone off.

A second operation controlled by the operation control logic 41 is theenabling of the five MC pushbuttons 42b through 42 which is accomplishedby an output of the operation control logic 41f transmitted to thepushbutton assembly 42, 43. The five MC pushbuttons are enabled onlywhen an output (CHOICE ENABLE, in FIG. 7) of operation control logic 41is high.

The MC pushbuttons are enabled:

(1) the tape recorder is stopped,

(2) an MC signal has been detected, and

(3 Neither of the RIGHT or WRONG indicator lamps is on.

As a result of these three conditions, pressing any of the MCpushbuttons has no effect when the tape recorder is playing, and alsoafter the recorder is stopped if no MC signal has been detected sincethe last time the recorder had been started. Also, after a RIGHT orWRONG indicator lamp comes on, pressing another MC pushbutton has noeffect until the light goes out again.

The operation of the mechanical pushbutton assembly 42 consisting of thesix pushbuttons 42a through 42 and the attached pushbutton assemblyprinted circuit board 43 has been described hereinabove except for themanner in which they operate if more than one MC pushbutton is pressed.Upon an MC pushbutton being premed, its output goes to the confirmationlogic 41g as the MC input. Thus, when one of the MC pushbuttons 42bthrough 42 is depressed in response to a multiple choice question,either the RIGHT or WRONG indicator lamp 44a or 44b becomes illuminated.

The five MC pushbuttons 4212 through 42. are electrically interlocked onthe pushbutton assembly printed circuit board 43 in a manner such thatif more than one pushbutton is pressed at a time, the lower numberedpushbutton takes priority and the system responds as if only onepushbutton was depressed.

A detailed block diagram of the mechanical pushbutton assembly 42 andthe pushbutton assembly printed circuit board 43 is illustrated in FIG.5. The six pushbuttons, START 42a and the five MC 4212 through 42 areattached to the printed circuit board 43 and the various operationsperformed by the circuitry on this board are indicated in FIG. 5 at theoutput of the particular elements on the board. Thus, the STARTpushbutton 42a is connected to a pulse forming circuit 43a such that theSTART signal is transmitted to the control logic 41 as a short pulseoccurring at the time the pushbutton is depressed.

The five MC pushbutton switches 42b through 42 are operative (enabled)only when the CHOICE EN- ABLE signal is received from the operationcontrol logic circuit 41 This CHOICE ENABLE signal is passed through onenormally closed contact 42 such that if more than one pushbutton ispressed at a time, only that pushbutton that occurs first in thesequence will produce an output. When the pushbutton is pressed (thecontact arms moving downward as illustrated in FIG. 5), the CHOICEENABLE signal is switched to the control logic 41 by way of an inverter43b. An inverter 43c inverts the polarity of the CHOICE ENABLE signal atthe output of OR gate 4H in FIG. 7 in order to provide the properpolarity for the MC switches.

Referring now to FIG. 6, there is shown a detailed block diagram of thecontrol track amplifier 40 indicated more generally in FIGS. 3a and 4.The amplifier portion 40a of control amplifier circuit 40 includes fourstages of amplification with the first stage 40a having a first inputsupplied from the record/playback (R/P) head of the tape recorder. Anautomatic level control (ALC) is provided by an attenuator between thefirst 40:1 and second stage amplifiers: 4011 by means of a feedback loopfrom the output of an emitter follower 40a connected to the output ofthe fourth stage amplifier. The emitter follower functions as an outputdriver and its output signal is also supplied to the CLOCK and DATAlevel detectors 40b and 46b The ALC feedback loop includes a rectifierand filter to provide a DC voltage to the attenuator. The positivepulses of the output signal of emitter follower 40a contain the CLOCKinformation, and the negative pulses contain the DATA information.

Referring now to FIG. 7, there is shown a detailed block diagram of thecontrol logic circuit 41 shown generally in FIG. 3a and with some detailin FIG. 4. The CLOCK signal from the output of clock level detector 40bin the control track amplifier circuit is supplied to inverter 41a whichcomprises a transistor. The output of inverter 41a provides the SET(S)input to a flip-flop 4111 and the m signal from the output of the datalevel detector 4011 provides the RESET(R) input thereto. The output offlip-flop 41a is the PWM format signal converted into a return-to-zerodigital signal and both polarities thereof are supplied to the 1-Kinputs of siX bit shift register 41:1 Shift register 41a is composed ofthree dual flip-flops. The C LOCK signal from the output of clock leveldetector 401: is also supplied to one-shot 4141 and upon triggeringthereof, produces a symmetrical square wave at the output thereof. Thenegative-going transition of this square wave produces an output pulseof about 2.0 microseconds duration upon passage through pulse formingcircuit 41a This short pulse at the output of circuit 41a is hereindesignated as the SAMPLE pulse, and it is supplied to the T input ofshift register 41a for clocking the digital data signal therethrough andthereby converting the return-to-zero output of flip-flop 41a to anonreturn-to-zero binary signal propagating through the shift register.

The word detector circuit portion of circuit 41b comprises AND gate 41bhaving two inputs supplied from the BITS 1 and 6 outputs of shiftregister 41a. When the two inputs are both high, the output of gate 41bis high when permitted by the delay gate portion 41b of the worddetector and delay circuit 41b and by inverter 4-lb connected to theoutput of inverter 41a The Word detector output from AND gate 41b issupplied to command detection NAND gates 410 41d 41 and 41i Secondinputs to NAND gates 41c 41d 41 and 41i are supplied from the BITS 2-5outputs of shift register 41a Thus, when the SLIDE advance code word isdetected, the gate 410 output goes low causing a transistor in one-shot416 to conduct thereby turning on the silicon controlled rectifier (SCR)which operates the slide projector to cause a single slide advance. Whenthe PRO]. 2 code word is detected, the gate 411 output goes low and caninitiate operation of the second visual dis play device (i.e., a movieprojector as one example.)

The tape recorder play control circuit 41d is basically a play flip-flop41d which is turned on and off to drive a transistor 41d that switchesthe tape recorder motor on and off. Play flip-flop 41:1 is set bydepressing the START pushbutton (PB), whose signal passes through thepulse forming circuit 43a (In FIG. 5) and gate 41d This setting may beinhibited by an INHIBIT input to gate 41d from an OR gate 411 in theoperation control logic circuit 41 to be described hereinafter. Thus,when the START input goes high, play flip-flop 41d sets and turns ondriver transistor 41d whereby the tape recorder motor is caused tooperate. Play flip-flop 41a! is reset by detection of a STOP word inNAND gate 41d In the case of the AUTO/ MANUAL switch 45 being in theMANUAL position, the motor control transistor 41d is bypassed and alltape recorder operations are controlled directly by the tape recorderpushbuttons a-e.

As stated hereinabove, the delay gate in circuit 41b illustrated in FIG.4 prevents the detection of an erroneous command during periods in whichthe digital signal is not in a steady-state condition. The delay gate41b includes transistor circuitry wherein the collector of one of thetransistors is connected to the common line output of AND gate 41b suchthat whenever this transistor is switched on, the output of AND gate 41bis held low and none of the command detection gates 410 41d 41 and 411'are allowed to operate.

A first holding action on the common line output of word detector ANDgate 411: occurs whenever the tape recorder starts or stops, and also atthe start of the recorded digital signal on the digital track due to thestart-up of the tape recorder in the programming unit, as mentionedhereinabove. The tape recorder start-up is controlled by delay gate 411;and is response to the CLOCK signal from the output of the clock leveldetector 40b When no CLOCK pulses are received, the transistor in thedelay gate circuit 41b is turned on and the common line output from ANDgate 41b is held low. The delay gate circuit 411; provides a slow-on,fast-off action such that cessation of the CLOCK pulses produces theholding action much quicker than the release of the holding action dueto the arrival of a CLOCK pulse, thereby minimizing possible errors dueto any gaps in the digital control signals which may have beenaccidentally or purposely placed in the taped program.

A second input to the transistor in the delay gate 41b is provided fromthe 6 output of play flip-flop 41d to turn on such transistor andthereby produce an immediate hold on the common line output of AND gate41b when NAND gate '41d detects a STOP command and is reset. This actionprevents the control logic from responding to any erroneous signalsproduced as the tape recorder is slowing down to a stop.

A second holding action on the common line output of word detector ANDgate 41b comes from inverter 41b which has a CLOCK signal input. Sincethe SAMPLE pulse which triggers (clocks) shift register 41a occurs at afixed time after the CLOCK pulse, the CLOCK pu se never goes high justat the time the shift register is clocked. Therefore, the CLOCK pulse isused by inverter 41b as a further hold on the common line output of gate41b to assure that it cannot go high unless the CLOCK pulse is alsohigh. This gating action prevents any possible false operation due tonormal time delays in the logic circuitry during shift registertransitions.

As the control signal is propagated through shift register 41a the BITS2 through 5 outputs thereof are passed through a quad latch 41c to theMULTIPLE CHOICE (MC) word decode gate 41e which responds to the fi MCword codes. Quad latch 412 comprises four flip-flops, and whenunlatched, passes BITS 2-5 directly through. When latched, quad latch41e holds the MC bits un l reset. As long as a latch signal at the 65output of latch flip-flop 41] in the operation logic circuit is high,the latch flip-flop is in the reset condition and the MC BITS 2-5outputs of shift register 41a pass directly through quad latch 41e Latchflip-flop 41a is present by a pulse from pulse forming circuit 41 theinput to circuit 41 being produced as play flip-flop 41d turns on. Thus,the first time the play flip-flop 41d is set, by the student pressingthe START pushbutton, the 6 output of the play flip-flop is transmittedto a first RESET input of latch flip-flop to reset it. Following an MCquestion, latch flip-flop 41) is reset by a second RESET input beingtriggered from the output of the RIGHT one-shot 41g in the RIGHTindicator lamp circuit of confirmation logic 41g thereby assuring thatthe MC pushbuttons 42b-f are disabled after a correct answer choice hasbeen made.

When any of the five MC word codes is detected, an output from gate 41eis supplied to OR gate 41f to thereby produce an output which issupplied to command detection NAND gate 41 The output of gate 41!: isnormally low and goes high when an MC word code i detected. If theoutput from the word detector AND gate 41b is also high, and all theother holds are removed, both inputs to NAND gate 41 are high and theoutput goes low to thereby produce an output to the SET input latchflip-flop 41 and cause the Q latch output thereof to go low. When the Qlatch signal is low, the quad latch 41a is latched and the states ofshift register BITS 2-5 outputs (i.e., the MC word codes) are held(stored) in the quad latch.

The five MC word codes are detected by gate 41e which is a conventionalone-of-eight binary decoder integrated circuit. The five outputs of MCgate 41e (which correspond to the five MC answers) are supplied to ANDgate 41g Five corresponding inputs to gate 41g are also provided fromthe five MC pushbuttons 4212-42 (after passing through inverter 43b asshown in FIG. 5). If a correct answer choice is made by the student, theoutput of AND gate 41g goes high and triggers the RIGHT oneshot 41gthereby turning on driver transistor 41g and causing the RIGHT indicatorlamp 44a to light for approximately three seconds, and also turning onpulsed driver transistor 41/1 for advancing the RIGHT counter 48a by onecount.

All of the MC pushbutton inputs are also supplied to an OR gate 41g sothat when any of the MC pushbutton inputs is received, this OR gateoutput goes high. The output of OR gate 41g triggers WRONG one-shot 41gif an INHIBIT signal from the RIGHT one-shot 41g is not present. Theoutput of one-shot 41g turns on driver transistor 41g to cause the WRONGindicator lamp 44b to light for approximately five seconds and alsoturns on pulsed driver transistor 41h for advancing the WRONG counter48b by one count. OR gate 41g responds each time an MC pushbutton inputis received, but WRONG one-shot 41g operates only when the wrong answerchoice has been made. Therefore, if the confirmation logic hasdetermined that the students answer choice is correct, the RIGHTone-shot 41g output will be high and provides an INHIBIT input to WRONGone-shot 41g to prevent the latter one-shot from being triggered.

When AUTO/ MANUAL switch 45 is in the MANUAL position, the RIGHT andWRONG one-shots 41g and 41g are prevented from being triggered by anINHIBIT input and thus neither RIGHT or WRONG indicator lamp is lit,dandneither RIGHT or WRONG counter is advance The operation control logiccircuit 411 provides the constraints on operation of the teaching systemto assure its proper use by the student. Two fundamental operations arecontrolled, namely, operation of the START pushbutton 42a and the fiveMC pushbuttons 42b'f. Each time the START pushbutton 42a is depressed,the START PB output from the pushbutton assembly is supplied to gate 41dHowever, an INHIBIT input to gate 41d from OR gate 41 determines whetherthe START signal will set the play flip-flop 41a? and start the taperecorder motor. This inhibiting action is provided by the presence (highstate) of any of three inputs to OR gate 41?. The first input to OR gate41f is the output of flip-flop 41f which is set by the output of NANDgate 41] which also sets flip-flop 41 As discussed hereinabove, gate4-11 provides an output when an MC word code is detected and flip-flop41 therefore remains in the reset condition until an MC word code isdetected. When flip-flop 41;" is set, it provides an input to OR gate411 which provides the INHIBIT input to gate 41x1 Flip-flop 41 remainsset until it is reset by a RESET signal from the output of AND gate 41gwhich goes high when the student makes the correct response to amultiple choice question. 'Flipflop 411" is therefore set when an MCword code is detected, and is reset for a correct answer to an MCquestion. The other two inputs to OR gate 41 come from the outputs ofthe RIGHT and WRONG one-shots 41g and 41g and thus provide that the taperecorder cannot be restarted until the RIGHT or WRONG indicator lampshave gone otf. Since these events provide a hold for the STARTpushbutton, it follows that the tape recorder cannot be restartedfollowing detection of an MC code until all the inputs to OR gate 41 areabsent (low).

The second operation controlled by the operation control logic 41 is theenabling of the five MC pushbuttons. This enabling operation is effectedby the CHOICE =EN- ABLE signal developed at the output of OR gate 41 andis supplied to the MC pushbuttons 'as seen in FIG. 5. The CHOICE ENABLEsignal is generated in OR gate 41 which receives inputs from playflip-flop 41d latch flip-flop 41 and the RIGHT and WRONG one-shots 41gand 41g Thus, the MC pushbuttons are enabled only when the tape recorderis stopped, an MC command has been detected and neither RIGHT or WRONGindicator lamp is on. The MC pushbuttons are disabled after a correctanswer to a question is made, since this causes the latch flip-flop 41]to reset (from the output of one-shot 41g thereby removing the CHOICEENABLE signal (i.e., it goes low) and provides that, after a correctanswer choice is made, no more choices may be made for that question.

'From the foregoing, it is readily apparent that the objectives setforth have been met. Thus, my invention provides a teaching systemhaying an audio, visual and student response capability provided by thetape recorder and response unit, and includes the totalling of thestudents right and wrong responses on electro-mechanical countersmounted on the response unit preferably out of view of the student. Theprogramming component is relatively simple to operate and therefore doesnot require extensive programming expertise on the part of theinstructor. These advantages are obtained primarily from my novel use ofa two track tape recording wherein selfclocking digital control signalsare recorded on one track, these self-clocking digital signals inconjunction with the response unit logic commanding various automaticoperations such as stopping the program at predetermined points,providing for responses to multiple choice questions With confirmationto the student of the correctness of his answer, and automaticallyadvancing slides in a slide projector interconnected with the responseunit. The response component is operated by the student and thus, theteaching system is especially well adapted for individualizedinstruction since each student may progress at his own speed. Themultiple-choice answers can obviously be less than five in number, ifdesired. Although a six-bit word code length has been described herein,other multi-bit word code lengths can be used, the particular bit lengthbeing primarily determined by the number of digital commands to beutilized in the program. Also, the bit number lengths of the multi-bitword code and number of stages of the multi-bit sequence generator 22 inthe control track signal generator need not necessarily be identical. Itshould be obvious that in the case of word code lengths of other thansix bits, the shift register 41a would have a bit capacity correspondingto the bits in the multi-hit word code, and the latch circuit 412 wouldhave a capacity of two bits less. It is, therefore, to be understoodthat changes may be made in the particular embodiment as described whichare within the full intended scope of the invention as defined by thefollowing claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:{

1. An audio-visual-response teaching system comprising a programmingcomponent and a response component, said programming component adaptedto be operated by an instructor and comprising a first two-track taperecorder and a programming unit, said rfirst two-track tape recordercomprising means for recording analog signals on a first track of a tapein the tape recorder wherein the analog signals represent an audioprogram to be presented to a student, said programming unit comprising,

a control panel provided with a first plurality of command pushbuttons,and means in communication with said first plurality of pushbuttons andsaid first tape recorder for continuously recordingpulse-width-modulated self-clocking digital control signals on a secondtrack of the tape, the digital control signals being of equal durationexcept at appropriate points in the audio program wherein the digitalsignals represent commands for automatic operations such as remotelyoperating a visual display device interconnected with said responsecomponent and stopping the tape after a question has been presented to astudent and for storing the correct answer of a plurality of answerchoices to the question, the instructor programming the digital signalsby depressing a selected one of said first plurality of pushbuttonscorresponding to the particular command to be recorded on the tape, saidresponse component adapted to be operated by the student and comprisinga second two track tape re corder and a response unit,

said second two-track tape recorder comprising means for detecting theanalog signals recorded on the first track of the tape whereby the audioprogram is presented to the student, said response unit comprising acontrol panel provided with a START pushbutton whereby the studentcontrols starting operations of the response component, and a secondplurality of MULTIPLE CHOICE answer pushbuttons, the student respondingto the question presented to him by depressing a selected one of saidMUL- TIPLB CHOICE pushbuttons to indicate his choice of an answerthereto, means in communication with said second tape recorder fordetecting the pulse-width-modulated self-clocking digital controlsignals continuously recorded on the second track of the tape, means incommunication with said digital control signal detecting means fordecoding the detected digital control signals to thereby decode thecorrect answer choice to the question and perform any other commandsdictated by the decoded digital signals, and ton operated, the output ofsaid multi-bit semeans in communication with said digital quencegenerator held in the logic ONE state signal decoding means and saidsecond pluat all times except when a command is entered rality ofpushbuttons for providing confir whereby each of the plurality ofmulti-bit Word mation to the student of the correctness or codes havelogic ONES as the first and last bits incorrectness of the studentsanswer choice. thereof, the bit number lengths of the multi-"bit 2. Theaudio-visual-response teaching system set forth word code and number ofstages of said sein claim 1 wherein quence generator not necessarilybeing the same. said means for continuously recording pulse-width-mod-6. The audio-visual-response teaching system set forth ulatedself-clocking digital control signals on the secin claim 2 wherein 0ndtrack of the tape comprises said control track signal generatorcomprises:

a control track signal generator in communication with said firstplurality of command pushbuttons for generating a particular multi-bitsequence de a free-running multivibrator, a six-bit sequence generatorclocked by said multivibrator,

fining a desired digital word code in response to a plurality of firstflip-flops corresponding to the the particular depressed commandpushbutton plurality of commands provided by the digital on the programunit control panel, the leading control signals, SET inputs of saidfirst flip-flops edge of each digital signal pulse being at theconnected to the corresponding first plurality of system CLOCKrepetition rate thereby includcommand pushbuttons on the programmingunit ing the CLOCK component and the pulse width control panel,determining the DATA component of the digital the plurality of commandpushbuttons also consignal, and nected to an input of an OR gate,

means in communication with an output of said output of said OR gateconnected to a SET input control track signal generator for transmittingof a second flip-flop, output of said second flipthe generated multi-bitsequence digital Word flop connected to a first input of a first ANDcode composed of pulse-width-modulated selfgate, output of said OR gatealso connected to clocking digital pulses to a record head in said a snd input f aid first AND gate whereby first tape recorder pon epr ssiono 3 an output of said first AND gate is inefiective CORD pushbutton 0nthe Program unit Control until the particular command pushbutton is re-Pahel, the RECORD pushbutton in Communicaleased, output of said firstAND gate connected tion with said first tape recorder.

to an ENABLE input of said six-bit sequence generator to cause saidsequence generator to produce a sixe'oit sequence output when thecommand pushbutton is released. 7. The audio-visual-response teachingsystem set forth in claim 6 wherein said control track signal generatorfurther comprises first logic circuit means in communication with saidprogramming unit command pushbuttons and said multi-bit sequencegenerator for producing a multi-bit sequence output therefrom upon oneof said command pushbuttons being depressed and released.

a like plurality of second AND gates having first inputs connected tooutputs of corresponding said first flip-flops and having second inputsconnected to outputs of said six-bit generator,

outputs of said plurality of second AND gates connected to a SET inputof a third flip-flop,

4. The audio-visual-response teaching system set forth in claim 3wherein said control track signal generator further comprises output ofsaid third flip-flop connected to a first input of a third AND gate,

a pulse-width generator producing a sequence of all logic ZEROES untilinterrupted at an appropriate point in the sequence, and

output of said six-bit sequence generator connected to a second input ofsaid third AND gate whereby a desired digital word code corresponding tothe particular depressed command pushsecond logic circuit means incommunication with button i b i d b gating th output of said saidmulti-bit sequence generator and said first six-bit sequence generatorth ough said third logic circuit means for gating the output of said ANDgate t an appropriate int in the se Imflti-bit Sequence generator at thepp p quence at which the desired word code appears, Point in thesequel'lce corresponding to the p an output of said third AND gateconnected to ticular command pushbutton operated, the gated a fi t;input f a l idth generator, said output of said multi-bit sequencegenerator in pulse width generator producing a sequence of communicationwith a first input of said pulsel logic ZEROES until interrupted at theWidth generator, Output of Said free-running propriate point in thesequence, output of said multivibrator connected to a second input offree-running multivibrator connected to a secsaid pulse-width generatorto provide at the out- 0nd input of said pulse-width generator to proputthereof a multi-bit sequence beginning with the desired multi-bit wordcode corresponding to the particular command pushbutton operated.

vide at the output thereof the desired six-bit se quence word code inpulse-width modulated self clocking digital form.

5. The audio-visual response teaching system set forth 8. Theaudio-visual-response teaching system set forth in claim 4 wherein inclaim 7 wherein said control track signal generator further comprisessaid control track signal generator further comprises third logiccircuit means in communication with said free-running multivibrator andsaid second logic circuit means for closing the gated output an outputof said third flip-flop connected to a first input of a fourth AND gate,output of said freerunning multivibrator connected to a second inof saidmulti-bit sequence generator after only a put of said fourth AND gatewhereby the outparticular plurality of pulse-width-modulated put of saidfourth AND gate is a gated clock pulses appear at the output of saidpulse-width signal,

generator whereby the output thereof is only a a divide-by-six counterhaving an input connected single desired multi-bit sequence word codecorto the output of said fourth AND gate and an responding to theparticular command pushbutoutput connected to the RESET input of said 17 third flip-flop whereby after six clock pulses, said divide-by-sixcounter resets said third flip-flop and thereby closes said third ANDgate thereby choice of the like plurality of answer choices to thequestion presented to the student.

response unit control panel START pushbutton connected to said taperecorder play control logic circuit for causing the tape recorder toturn on,

permitting only six pulse-width-modulated and pulses to appear at theoutput of said pulsethe decoding of a MULTIPLE CHOICE word widthgenerator, code in said word decode logic circuit storing said digitalcontrol signal being of the pulsetherein the correct answer choice tothe queswidth-modulated type, output of said six-bit setion Presented tothe tqnenee generator h ld i h l i ONE state t 13. Theaudio-visual-response teaching system set forth all times except when acommand is entered in e m 12 w e ein whereby each of the plurality ofsix-bit Word sa1d WOrd decode logic circuit Comprising codes h l i O Sas h fi t d i h bi a latch circuit having inputs connected to theinterth fl mediate bit stages of said shift register, and 9. Theaudio-visual-response teaching system set forth a {nulti-inpllt,multi-outpllt gate Circuit, e multii l i 1 h i 15 inputs thereofconnected to outputs of sa1d latch said programming unit control panelcommand pushclrcl'llt Whlch Pmvlde thePmTahtY of multiple buttonscomprise choice answer word code bits, and

a pushbutton providing a command signal for inian QPeratlOn PIOgICFITCUit including latch tiating operation of the visual displaydevice, P" P hill/111g a SET lnpllt Q0I}1m11{11'3ati0fl a STOPpushbutton providing a command signal with the P the gate clrclllt 111 dWord fo Stepping h Second tape recorder at the a1) decode logic circuit,output of sa1d latch flip-flop propriate points i h di program, andconnected to a LATCH input of said latch cira plurality of MULTIPLECHOICE answer pushcult whereby said lat-Ch P' P becomes Set buttons, oneof which is selected by the instrucwhen any of the P Word o es is tor frepresenting h one correct answer detected and thereby causmg sa1d latchcircuit to hold the data contained .in the intermediate bits until resetby a signal developed in a confirmation logic circuit after the studentselects the correct answer choice. 14. The audio-visual-responseteaching system set forth in claim 13 and further comprising aconfirmation logic circuit connected to outputs of said word decodelogic circuit and comprising 10. The audio-visual-response system setforth in claim 1 wherein said means for detecting the analog signalsbeing play- 3 back means supplying audio signals to a pair of earphonesutilized by the student whereby the teaching system is adapted forindividualized instruction. 11. The audio-visual-response teachingsystem set forth a plurality of AND gates having first inputs 6011' inclaim 2 wherein nected to the outputs of said word decode logic saidmeans for detecting the digital control signals comcircuit multi'inpubmulti-output gate Circuit and prising a control track amplifier havingan input connected to the playback head of said second tape recorder,said control track amplifier including a second inputs connected to theplurality of MULTIPLE CHOICE bushbuttons on said response unit controlpanel,

the MULTIPLE CHOICE pushbuttons also conpair of level detectors fordetecting positive and 40 nected to multiple p of an OR gate, negativeportions of the digital signal and there- Outputs of Said confirmationlogic Circuit AND by reconstructing th CLOCK d DATA gates and OR gateconnected respectively to first ponents of the pulse-width-rnodulatedself-clockinputs of first and Second OHe'ShOlS, j di it l control i l ath outputs th eof outputs of said first and second one-shots in comamulti-bit shift register circuit having J-K inputs mllnication WithRIGHT and WRONG p connected to the DATA output of said control output ofsaid first one-shot also connected to track amplifier and having atrigger input conan INHIBIT second input of said second onenected to theCLOCK output of said control shot, track amplifier, and r the studentschoice of an answer as indicated by a word detector and delay gatecircuit, the word 00 the particular depressed MULTIPLE CHOICE detectorthereof having inputs connected to the pushbutton on said response unitcontrol panel first and last bit outputs of said shift register, beingcompared in said AND gates with the corthe logic ONE state output of theword detector rect answer stored in said word decode logic cirbeingproduced only when the first and last bits cuit multi-input,multi-output gate, a correct anare simultaneously logic ONE to therebysatisfy swer response by the student causing said cona criteria fordetection of a valid command word code.

firmation logic circuit AND gate to trigger said first one-shot andlight said RIGHT lamp there- 12. The audio-visual-response teachingsystem set forth in claim 11 wherein said means for decoding thedetected digital control sig- 6O nals comprises a slide advance logiccircuit, a tape recorder play control logic circuit, and a word decodelogic circuit, outputs of the shift register stages intermediate thefirst and last bits and the output of said word detector connected toinputs of said slide advance, tape recorder play control and word decodelogic circuits, the decoding of a slide advance command word code insaid slide advance logic circuit causing the visual display device tooperate, the decoding of a STOP command word code in said tape recorderplay control logic circuit causing the second tape recorder to turn off,said by confirming to the student the correctness of his answer choiceand also inhibiting said second one-shot to prevent said WRONG lamp frombeing lit, an incorrect answer response causing said confirmation logicOR gate to trigger said second one-shot to thereby light said WRONGlamp.

15. The audio-visual-response teaching system set forth in claim 14 andfurther comprising an output of said confirmation logic first one-shotconnected to a first RESET inputof said operation control logic latchflip-flop,

a second RESET input of said latch fiipflop in communication with saidtape recorder play control logic circuit whereby the data. contained inthe intermediate bits is held in the latch circuit until the taperecorder has stopped and the: student has made the correct answerresponse to the multiple choice quesbuttons, the student responding to aquestion tion. presented to him by depressing a selected one of 16. Theaudio-visual-response teaching system set forth said MULTIPLE CHOICEpushbuttons to inin claim 15 and further comprising dicate his choice ofan answer thereto,

a first electro-rnechanical counter in communication means incommunication with said tape recorder with the output of saidconfirmation logic first onefor detecting pulse-width-modulatedself-clockshot, and ing digital control signals continuously recorded asecond electro-mechanical counter connected to the on the second trackof the tape wherein the output of said confirmation logic secondone-shot, digital control signals are of equal duration exsaid firstcounter providing a total of the students cept at appropriate points inthe audio procorrect answer responses and said second counter programand represent particular commands, viding a total of the studentsincorrect answer means in communication with said digital control signaldetecting means for decoding the detected responses. 17. Theaudio-visual-response teaching system set forth digital control signalsto thereby decode a correct in claim 12 wherein 15 answer choice to thequestion and perform any the delay gate having a first input from theCLOCK other commands dictated by the decoded digital output of saidcontrol track amplifier, said delay gate responding to the CLOCK pulsesand if none are being received, the delay gate holding the output of theword detector both when the tape recorder is stopped and when the tapeis moving but there is signals, and

means in communication with said digital signal decording means and saidsecond plurality of pushbuttons for providing confirmation to thestudents of the correctness or incorrectness of no recorded signal onthe digital track, the arrival of the students answer choice. a CLOCKpulse causing said delay gate to produce a 21. A programming componentadapted for use in an delay before the hold is removed from the worddeaudio-visual-response teaching system and to be operated tector outputto thereby prevent the detection of 2 by an instructor and comprisingerroneous commands during periods in which the a two-track tape recorderand a programming unit, digital signal is not in a steady statecondition. said two-track tape recorder comprising 18. Theaudio-visual-response teaching system set means for recording analogsignals on a first track forth in claim 17 and further comprising of atape in the tape recorder wherein the analog a second input to saiddelay gate from said tape signals represent an audio program to berecorder play control logic circuit for prevention of presented to astudent, detection of an erroneous command during the slowsaidprogramming unit comprising, down condition of the tape recorder when itis being a control panel provided with a plurality of comstopped, thedetection of a STOP command in said mand pushbuttons, and tape r rd r ply Control logic cirCllit P d g means in communication with saidplurality of pushan immediate hold on the output of the word debuttonsand said tape recorder for continuously tector. recordingpulse-width-modulated self-clocking digital 19. Theaudio-visual-response teaching system set forth control signals on asecond track of the tape, the in claim 15 and further comprising digitalcontrol signals being of equal duration exsaid operation control logiccircuit having inputs in cept at appropriate points in the audio programcommunication with the output of said delay gate, o d the output of saidword decode logic gate circuit and said confirmation logic circuit, andhaving an output connected to an INHIBIT input of said tape wherein thedigital signals represent for automatic operations such as remotelyoperating a visual display device interconnected with said responsecomponent and stopping the tape after a recorder play control logiccircuit to prevent restart question has been presented to a student andfor of the tape recorder motor upon detection of a storing the correctanswer of a plurality of answer MULTIPLE CHOICE word code until thestudent choices to the question, the instructor programming selects thecorrect answer response. the digital signals by depressing a selectedone of said 20. A response component adapted for use in anaudioplurality of pushbuttons corresponding to the pa visual-responseteaching system and to be operated by a o tioular command to be recordedon the tape. student and comprising a two-track tape recorder and aresponse unit, References Cited said two-tracfk tatpetricorderclomprising d d UNITED STATES PATENTS means or e ec mg ana og signasrecor e on the first track of the p by an audio p TlllOtSOl'l et al. A3,509,549 4/1970 Ohta et al. 340174.1 H

gram is presented to the student, said response unit comprising acontrol panel provided with a START pushputton whereby the studentcontrols starting operation of the response component, and a pluralityof MULTIPLE CHOICE answer push- WILLIAM H. GRIEB, Primary Examiner US.(:1. X.R.

